High-Strength Copper Alloy

Abstract

 The present invention is a high strength copper alloy that is superior in mechanical properties, workability, corrosion resistance and economical efficiency. The present invention discloses high strength copper alloy characterized in that said copper alloy consists essentially of 4 to 17 mass percent of Zn, 0.1 to 0.8 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 • Si=2 to 15 mass percent; average grain size D of the microstructure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to the high strength copper alloy suitable for materials comprising leads, switches, connectors, relays and sliding pieces etc. which are parts of electrical devices, electronic devices, communication equipments, information appliances, measuring instruments, automobiles and so on.

2. Prior Art

[0002] In general, high strength copper alloys are used as materials comprising leads, switches, connectors, relays and sliding pieces etc., which are used as parts of electrical devices, electronic devices, communication devices, information appliances, measuring instruments, automobiles, and so on. Recently, devices have been improved toward miniaturization, lightweighting, and higher efficiency, so that there are extremely severe demands for the improvements of characteristics of the materials. For example, extremely thin plates are employed for spring contact members of connectors. higher strength is required for the high strength copper alloys comprising said extremely thin plates in order to thin the plates still more. It is also demanded for high strength copper alloys to be better balanced between strength and ductility including bending characteristics, to have superiority in productivity and economical efficiency, and to have no problem with conductivity, corrosion resistance (against stress, dezincification and migration), stress relaxation characteristics, solderability, wear resistance and so on.

[0003] Incidentally, beryllium copper, titanium copper, aluminum bronze, phosphor bronze, nickel silver, yellow brass and brass doped with Sn or Ni are generally well-known as high strength copper alloys. However, there are following problems for these high strength copper alloys, so that it was impossible to satisfy the above demands.
beryllium copper has the highest strength in copper alloys, but beryllium is extremely harmful to the humans: in particular the beryllium vapor in fusion state is significantly dangerous for the humans even in a very small amount, so that initial cost of melting facilities becomes extremely expensive because of difficulty in disposal processes, particularly in incineration of the beryllium copper materials or their products. Therefore, since solution heat treatment at the final stage of production is required for beryllium copper to obtain the predetermined characteristics, the problems appear in economy including the manufacturing cost.

[0004] Titanium copper shows the second highest strength next to beryllium copper, but, again, expensive melting facilities are required because titanium is an active element, and hence it becomes difficult to keep quality and yield in the melting. As well as beryllium copper, since solution heat treatment becomes necessary at the last step of manufacturing, the problems in economy also appear.

[0005] For aluminum bronze, it is difficult to obtain sound ingots because aluminum is an active element, and furthermore aluminum bronze has lower solderability.

[0006] Phosphor bronze and nickel silver have poor hot workability, and are difficult to be produced by hot rolling. These alloys are usually produced with horizontal continuous casting. Consequently, these alloys are inferior in productivity, yield and energy cost. Additionally, as to a spring phosphor-bronze and a spring nickel-silver which are representative copper alloys with high strength, problems in economy appear because expensive Sn and Ni are abundantly contained in these two alloys.

[0007] Yellow brass and brass doped with Si and Ni are inexpensive, but there are problems with respect to their strength and corrosion resistance such as stress corrosion cracking and dezincification, and then they are unsuitable for the parts to realize miniaturization and higher efficiency.

[0008] As a result, these conventional high strength copper alloys are not satisfactory as materials for the parts used in the various devices with tendency toward miniaturization, lightweighting and higher efficiency, so that the development of a new high strength copper alloy is demanded greatly.

SUMMARY OF THE INVENTION

[0009] Present inventors have paid their attention to the Hall-Petch relationship (E. O. Hall, Proc. Phys. Soc. London. 64 (1951) 747. and N.J. Petch, J. Iron Steel Inst. 174 (1953) 25.) that 0.2% yield strength is proportional to grain size (D^-1/2), where said 0.2% yield strength is defined by the strength when permanent strain becomes 0.2%.

This 0.2% yield strength is also called "proof stress" hereinafter. The present inventors have (considered) developed the idea that the high strength copper alloys satisfying the demands of the times can be obtained by grain refinement, and then performed several investigations and experiments on grain refinement. From their results, it is found that the micronization for crystal grains (grain refinement) of copper alloys is realized by adding suitably selected elements in the recrystallization. It is recognized that the strength including mainly 0.2% yield strength is improved remarkably by making the grain size smaller to a certain level and its strength also increases with decreasing of the grain size. Furthermore, from the results of various experiments with respect to the influence of additive elements for grain refinement, it is clarified that the addition of Si to Cu-Zn alloys increases the number of nucleation sites and the addition of Co to Cu-Zn-Si alloys suppresses the grain growth. This means that Cu-Zn-Si or Cu-Zn-Si-Co alloy systems with fine grains are obtained by utilizing such effects.
In other words, the increase of nucleation sites is considered to be due to decreasing of stacking fault energy based on the addition of Si , and the suppression of the grain growth is considered to be due to the formation of fine precipitates based on the addition of Co. The present invention is completed based upon these investigated results and relates to the new high strength copper alloy (hereby claimed), which is superior in mechanical properties, workability and corrosion resistance without problems in economy. In particular the invention is suitable as materials for the parts composing several devices in tendency of miniaturization, lightweighting and higher efficiency. Accordingly, it is the object of the present invention to provide new high strength copper alloy that is extensively applied and extremely practical.

[0010] Namely, it is mainly first object of the present invention to provide the high strength copper alloy (called "first invention copper alloy") suitable for rolled materials (plates, rods and wires etc.) for which high strength is required (rolled materials which require high strength) or materials worked out of said rolled materials (press-formed products and bending-worked products etc.). Parts and products suitably manufactured by use of first invention copper alloy include: portable or miniature communication equipments which require thinization (to thin the plate still more) and lightweighting, electronic device parts used for personal computer, medical care instrument parts, accessory parts, machine parts, tubes or plates of heat exchanger, cooling instruments using sea water, parts composing inlet or outlet of sea water in small -sized ships, wiring tool parts, various instrument parts for automobile, measuring-instrument parts, play tools, daily necessities and so on. These are, concretely, connectors, relays, switches, sockets, springs, gears, pins, washers, coins for game machines, keys, tumblers, buttons, hooks, braces, diaphragms, bellows, sliding pieces, bearings, sliding pieces adjusting sound volume, bushes, fuse grips, lead frames, gauge boards and so on.

[0011] It is mainly second object of the present invention to provide the high strength copper alloy (called "second invention copper alloy") suitable for rolled materials (plates, rods and wires etc.) or the materials worked out of said rolled materials (press-formed products and bending-worked products etc.) which require highly balanced strength and electric conductivity,
where strength is not necessarily required to the same extent as first invention copper alloy. Parts and products suitably manufactured by use of second invention copper alloy include: electronic device parts which require electric conductivity, measuring-instrument parts, household electric appliance parts, tubes or plates of heat exchanger, cooling instruments using sea water, parts composing inlet or outlet of sea water in small -sized ships, machine parts, play tools, daily necessities and so on.

[0012] These are, concretely, connectors, switches, relays, bushes, fuse grips, lead frames, wiring instruments, keys, tumblers, buttons, hooks, braces, diaphragms, bellows, sliding pieces, bearings, coins for game machines and so on.

[0013] It is mainly third object of the present invention to provide the high strength copper alloy (called "third invention copper alloy") suitable for wire drawing materials [general wire materials of round cross section and deformed wire materials such as rectangle cross section (square etc.), polygon cross section (hexagon etc.) and so on] or materials worked out of said wire drawing materials (bending -worked products etc.),
where strength is required to the same extent as first invention copper alloy. Parts and products suitably manufactured by use of third invention copper alloy include: electronic device parts, parts for construction, accessory parts, machine parts, play tools, various instrument parts for automobile, measuring-instrument parts, electronic device parts and electrical device parts. These are, concretely, connectors, keys, headers, nails (nails for play instrument), washers, pins, screws, coiled springs, lead screws, shafts of copying machines etc., wire gauzes (wire gauze for culture or filter for inlet and outlet of seawater used in seawater cooling equipment and small ship etc.), sliding pieces, bearings, bolts and so on.

[0014] The first invention copper alloy consists essentially of 4 to 19 mass percent (preferably 6 to 15 mass percent, more preferably 7 to 13 mass percent) of Zn, 0.5 to 2.5 mass percent (preferably 0.9 to 2.3 mass percent, more preferably 1.3 to 2.2 mass percent) of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 · Si=0 to 15 mass percent (preferably 1 to 12 mass percent, more preferably 2 to 9 mass percent); average grain size D of the microstructure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 2.5 µm, more preferably 0.3 µm ≦ D ≦ 2 µm); and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).

[0015] In addition, the second invention copper alloy consists essentially of 4 to 17 mass percent (preferably 5 to 13 mass percent, more preferably 6 to 11.5 mass percent) of Zn, 0.1 to 0.8 mass percent (preferably 0.2 to 0.6 mass percent, more preferably 0.2 to 0.5 mass percent) of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 · Si=2 to 15 mass percent (preferably 4 to 12 mass percent, more preferably 5 to 10 mass percent); average grain size D of microstructure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 3 µm, more preferably 0.3 µm ≦ D ≦ 2.5 µm); and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).

[0016] Furthermore, the third invention copper alloy consists essentially of 66 to 76 mass percent (preferably 68 to 75.5 mass percent) of Cu, 21 to 33 mass percent (preferably 22 to 31 mass percent) of Zn and 0.5 to 2 mass percent (preferably 0.8 to 1.8 mass percent, more preferably 1 to 1.7 mass percent) of Si, wherein said mass percent of Cu, said mass percent of Zn and said mass percent of Si satisfy the relationships Cu-5 · Si=62 to 67 (preferably Cu-5 · Si=63 to 66.5 mass percent) and Zn+6 · Si = 32 to 38 (preferably Zn + 6 · Si=33 to 37 mass percent); average grain size D of the microstructure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm (preferably 0.3 µm ≦ D ≦ 3 µm, more preferably 0.3 µm ≦ D ≦ 2.5 µ m); and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm² (preferably higher than 300N/mm²).
In order to obtain said each invention copper alloy, there are some cases receiving a plurality of recrystallization treatments in which a part or all of the alloy structure is recrystallized by heat treatment. In such cases, said average grain size D and said 0.2% yield strength in a copper alloy are determined by the grain size and the 0.2% yield strength of the materials (called "recrystallized materials") obtained from the very last recrystallization treatment (called "last recrystallization treatment").

[0017] In the case that recrystallization treatment is performed only once, it goes without saying that such recrystallization treatment is the last recrystallization treatment and the treated materials are the recrystallized materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] Each invention copper alloy is provided with any form shown in the following preferred embodiments.

(Embodiment 1)

[0019] Ingots are worked into plastic worked materials with predetermined forms by plastic working including hot working (rolling, extruding and forging etc.) and/or cold working (rolling and wire drawing etc.). The plastic worked materials receive recrystallization treatment (last recrystallization treatment) based upon heat treatment (annealing etc.) in the range of the recrystallization temperature, and then become the recrystallized materials. Such recrystallized materials are rolled materials in first and second invention copper alloys, and wire drawing materials in third invention copper alloy.

(Embodiment 2)

[0020] The recrystallized materials of said embodiment 1 are worked into cold worked materials with predetermined forms by cold working (rolling, wire drawing and forging). Such cold worked materials are rolled materials in first and second invention copper alloys, and wire drawing materials in third invention copper alloy.

(Embodiment 3)

[0021] The recrystallized materials of said embodiment 1 are worked into manufactured materials with predetermined forms by press working or bending etc.

(Embodiment 4)

[0022] The cold worked materials of said embodiment 2 are worked into manufactured materials with predetermined forms by press working or bending etc.

[0023] In order to improve the properties of first invention copper alloy, it is desired for the copper alloy composition to contain 0.005 to 0.5 mass percent (preferably 0.01 to 0.3 mass percent, more preferably 0.02 to 0.2 mass percent) of Co and/or 0.03 to 1.5 mass percent (preferably 0.05 to 0.7 mass percent, more preferably 0.05 to 0.5 mass percent) of Sn.

[0024] In this case, the contents of Co and Sn are determined within said each range under consideration of the content of Si. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.05 to 0.5 (preferably Co/Si=0.01 to 0.3, more preferably Co/Si=0.03 to 0.2), wherein the value of Co content divided by Si content is defined as Co/Si. Additionally, the content of Sn is determined to satisfy the relationship Si/Sn≧ 1.5 (preferably Si/Sn ≧2, more preferably Si/Sn ≧ 3), wherein the value of Si content divided by Sn content is defined as Si/Sn.

[0025] In first invention copper alloy, it is possible for the copper alloy composition to contain 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) of Fe and/or 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) of Ni in substitution for Co or together with Co.

[0026] For said composition, the content of Fe or Ni is determined under consideration of the content of Si. In case Co is co-added, the contents of Si and Co are considered. Namely, the content of Fe or Ni is determined to satisfy the relationship (Fe+Ni+Co) /Si =0.005 to 0.5 (preferably (Fe+Ni+Co) /Si =0.01 to 0.3, more preferably (Fe+Ni+Co) /Si =0.03 to 0.2), wherein the value of total contents containing Co divided by Si content is defined as (Fe+Ni+Co) /Si. It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.55 mass percent (preferably 0.01 to 0.35 mass percent, more preferably 0.02 to 0.2 mass percent).

[0027] In order to improve the properties in second invention copper alloy, it is preferable to contain 0.005 to 0.5 mass percent of Co (preferably 0.01 to 0.3 mass percent, more preferably 0.02 to 0.2 mass percent) and/or 0.2 to 3 mass percent of Sn (preferably 1 to 2.6 mass percent, more preferably 1.2 to 2.5 mass percent) in alloy composition. In this case, the contents of Co and Sn are determined by considering their relations to Si content. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.02 to 1.5 (preferably Co/Si=0.04 to 1, more preferably Co/Si=0.06 to 0.5) within the range described above. In addition, the content of Sn is determined to satisfy the relationship Si/Sn ≦ 0.5 (preferably Si/Sn ≦ 0.4, more preferably Si/Sn ≦ 0.3) within the range described above.

[0028] In second invention copper alloy, it is possible to contain 0.005 to 0.3 mass percent of Fe (preferably 0.01 to 0.2 mass percent) and/or 0.005 to 0.3 mass percent ofNi (preferably 0.01 to 0.2 mass percent) in substitution for Co or together with Co. In this case, the content of Fe or Ni is determined by considering the content of Si (or both contents of Si and Co in case of co-addition). In other words, the contents of Fe and Ni are determined to satisfy the relationship (Fe+Ni+Co) /Si =0.02 to 1.5 (preferably (Fe+Ni+Co) /Si =0.04 to 1, more preferably (Fe+Ni+Co) /Si =0.06 to 0.5). It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.55 mass percent (preferably 0.01 to 0.35 mass percent, more preferably 0.02 to 0.25 mass percent).

[0029] Furthermore, for first and second invention copper alloys, it is possible to contain at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf corresponding to the characteristics required in their applications.

[0030] The contents of these elements are determined appropriately within the range of 0.003 to 0.3 mass percent.

[0031] In order to improve the properties of third invention copper alloy, it is preferable to contain 0.005 to 0.3 mass percent of Co (preferably 0.01 to 0.2 mass percent, more preferably 0.02 to 0.15 mass percent) and/or 0.03 to 1 mass percent of Sn (preferably 0.05 to 0.7 mass percent, more preferably 0.05 to 0.5 mass percent) in alloy composition.

[0032] In this case, the contents of Co and Sn are determined by considering the content of Si within above range. In other words, the content of Co is determined to satisfy the relationship Co/Si=0.005 to 0.4 (preferably Co/Si=0.01 to 0.2, more preferably Co/Si=0.02 to 0.15). In addition, the content of Sn is determined to satisfy the relationship Si/Sn ≧ 1 (preferably Si/Sn ≧ 1.5, more preferably Si/Sn ≧ 2).

[0033] For the third invention copper alloy, it is possible to contain Fe of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) and/or Ni of 0.005 to 0.3 mass percent (preferably 0.01 to 0.2 mass percent) in substitution for Co or together with Co.

[0034] In this case, the content of Fe or Ni is determined by considering the content of Si (or both contents of Si and Co in case of co-addition). In other words, the contents of Fe and Ni are determined to satisfy the relationship (Fe+Ni+Co) /Si =0.005 to 0.4 (preferably (Fe+Ni+Co) /Si =0.01 to 0.2, more preferably (Fe+Ni+Co) /Si =0.02 to 0.15). It is desirable for such determination that said total content (Fe+Ni+Co) is adjusted to be 0.005 to 0.35 mass percent (more preferably 0.01 to 0.25 mass percent, much more preferably 0.02 to 0.2 mass percent).

[0035] Furthermore, in alloy composition for third invention copper alloy, it is possible to contain at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf corresponding to the characteristics required in their applications,
where each content of P, Sb, or As is 0.005 to 0.3 mass percent and each content of Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In or Hf is 0.003 to 0.3 mass percent, and the total content, in case at least one of P, Sb or As is selected, is 0.005 to 0.25 mass percent.

[0036] By the way, as stated earlier, strength, particularly 0.2% yield strength, is enhanced by grain (recrystallized grain) refinement. The present inventors have confirmed experimentally that the 0.2% yield strength is enhanced remarkably when average grain size becomes smaller than 3.5

in comparison with larger than 3.5 □m. In addition, by reducing gradually average grain size D from 3.5 □m, it is identified that the enhanced ratio of proof stress increases rapidly at 3, 2.5 and 2 □m. From such experimental results, it is found that proof stress (generally higher than 250N/mm², preferably higher than 300N/mm²) required for the parts of electrical devices, electronic devices, communication equipments and measuring instruments is ensured (only) when average grain size D being smaller than 3.5 □m. In the case of demanding higher strength (proof stress), it is preferable for average grain size D to be less/smaller than 3.0 □m, and in the case of demanding still higher strength, it is preferable to be less/smaller than 2.5 □m. In order to improve drastically the strength within the possible range, it is preferable for average grain size D to be less/smaller than 2 □m. On the other hand, although proof stress is improved with decrease of average grain size D, it is anticipated to face difficulties in the practical realization of grain size less than 0.3 □m because the smallest grain size confirmed by the experiments is 0.3 □m.

[0037] From such points, in order to ensure the proof stress higher than 250N/mm² (preferably higher than 300N/mm²) in first, second and third invention copper alloys, the recrystallized structure of 0.3 µm≦D≦3.5 µm is required. In other words, it is necessary that average grain size D in the recrystallization state (state after the last recrystallization treatment) distributes in 0.3 µm ≦ D ≦ 3.5 µm and 0.2% yield strength is higher than 250N/mm². In the case of demanding higher strength for the second and third invention copper alloys, it is preferable to distribute in 0.3 µm ≦ D ≦ 3 µm, and more preferable to distribute in 0.3 µm ≦ D ≦ 2.5 µm. On the other hand, in the first invention copper alloy which requires even higher strength than the second and third invention copper alloys, depending on their applications, it is preferable to distribute in 0.3 µm ≦ D ≦ 2.5 µm, and more preferable to distribute in 0.3 µm≦D≦2 µm.

[0038] Additionally, in the first to third invention copper alloys of which grain refinement is realized by recrystallization due to the suitable heat-treatment (generally annealing), such grain refinement becomes possible (only) in the alloy composition described above.

[0039] Namely, in the first to third invention copper alloys, Zn and Si cause the stacking fault energy to decrease, the dislocation density to increase, and the nucleus sites of recrystallized grain generation to increase. Such functions which contribute to the grain refinement and the material strengthening due to solid solution into the Cu matrix (both functions are called "grain refinement and strengthening" hereinafter) are given, and the contents of those elements are determined by said ranges as mentioned below. For first and second invention copper alloys used mainly as rolled materials or their manufactured materials, when the functions of grain refinement and strengthening due to the addition of Zn appear enough, the content of Zn is more than 4 mass percent, and in order to improve largely the strength in first invention copper alloy, it is required that the content is more than 6 mass percent (preferably higher than 7 mass percent). For second invention copper alloy of which strength is allowed to be inferior to the first invention, it is preferable that the content of Zn is more than 5 mass percent (more preferably higher than 6 mass percent). On the other hand, when the content of Zn becomes excessive, the susceptibility to stress-corrosion cracking increases and the bending characteristic deteriorates. Accordingly, when the relation to the content of Si for the applications of the rolled materials and the inhibition function for stress corrosion cracking is taken into consideration, the content of Zn in the first invention copper alloy is less than 19 mass percent (preferably less than 15 mass percent, more preferably less than 13 mass percent), and the content in the second invention copper alloy is less than 17 mass percent (preferably less than 13 mass percent, more preferably less than 11.5 mass percent).

[0040] On the other hand, although the grain refinement and strengthening functions appear remarkably with much slighter addition of Si compared to Zn, such functions are caused by the interaction with Zn. In addition, Si improves the characteristics of the stress-corrosion cracking resistance by co-addition of Zn. On the other hand, the excessive addition of Si decreases the electric conductivity of this invention alloy. When these points are taken into consideration, it is required that the content of Si is higher than 0.5 mass percent (preferably higher than 0.9 mass percent and more preferably, 1.3 mass percent) for first invention copper alloy which accomplishes the strength improvement and grain refinement. However, the electric conductivity, hot workability and cold workability in first invention copper alloy are decreased by the Si content (also called the content of Si) in excess over 2.5 mass percent. Therefore, in order to keep those characteristics enough, it is preferable that the Si content is less than 2.3 mass percent, and the more preferable content is less than 2.2 mass percent.

[0041] On the other hand, in second invention copper alloy where the balance between the strength and electric conductivity is important, in order to realize the grain-refinement effect to achieve the predetermined strength, at least 0.1 mass percent of Si is necessary, and it is preferable to be higher than 0.2 mass percent. However, in order to ensure the predetermined electric conductivity considering its balance with strength, it is required that the Si content is less than 0.8 mass percent, and in order to ensure the electric conductivity enough to be used for the applications, it is preferable to be less than 0.6 mass percent (more preferably less than 0.5 mass percent).
Furthermore, in first and second invention copper alloys, it is necessary that the balance among the effect of grain refinement by the co-addition of Zn and Si, stress-corrosion cracking characteristics and the strength is kept, but it is unsuitable in these alloys to determine independently the individual content within said ranges. Accordingly, it is necessary that the relation between the Zn and Si contents is specified as Zn-2.5 · Si, and the values of this formulae are determined to be in above predetermined range. In order to obtain the predetermined strength based upon the grain refinement, it is necessary for first invention copper alloy to satisfy the relationship Zn-2.5 · Si ≧0 mass percent (preferably Zn-2.5 · Si ≧1 mass percent and more preferably Zn-2.5 · Si ≧ 2 mass percent ), and it is necessary for second invention copper alloy to satisfy the relationship Zn-2.5 · Si ≧ 2 mass percent (preferably Zn-2.5· Si ≧ 4 mass percent and more preferably Zn-2.5 · Si ≧ 5 mass percent ). On the other hand, in any of first and second invention copper alloys, it is necessary to satisfy the relationship Zn-2.5 · Si ≦ 15 mass percent because the stress corrosion cracking arises remarkably at Zn-2.5 · Si >15 mass percent. In order to inhibit effectively the stress corrosion cracking, it is preferable to satisfy the relationship Zn-2.5 . Si ≦ 12 mass percent (more preferably Zn-2.5 · Si ≦ 9 mass percent for first invention copper alloy, and Zn-2.5 · Si ≦ 10 mass percent for second invention copper alloy).

[0042] In addition, for the Zn content in third invention copper alloy, the grain refinement and strength are rightly considered as well as in first and second invention copper alloys. Furthermore, since the third invention copper alloy is mainly used as wire drawing materials and their manufactured materials, the Zn content should be determined in consideration of hot extruding characteristics, so that the Zn content is set to be abundant in comparison with first and second invention copper alloys. In order to ensure the hot extruding characteristics enough, it is necessary for Zn content to be higher than 21 mass percent. It is more preferable for Zn content to be higher than 22 mass percent so that hot extruding-wire drawing can be kept more excellent. Although stress-corrosion cracking resistance of third invention copper alloy is inferior in comparison with first and second invention copper alloys, it is still satisfactory to be used as wire materials etc. because Zn content of third invention alloy is still less than that of general Cu-Zn system alloys (for example, JIS-C2700 (65Cu-35Zn)).

[0043] However, in order to ensure enough stress-corrosion cracking resistance and cold workability, it is required that Zn content of third invention copper alloy is lower than 33 mass percent. In other words, when Zn content is higher than 33 mass percent,

and

phases are easy to remain in the structure and give an adverse effect upon the cold workability. Furthermore, the stress corrosion cracking and dezincification become also problems. In order to carry out the hot extrusion-wire drawing efficiently while the stress corrosion cracking resistance and the cold workability are ensured, it is preferable for Zn content to be less than 31 mass percent. In order to ensure the hot extrusion characteristics and the cold workability, it is also necessary in third invention copper alloy to consider the Cu content, and the □ and □ phases are easy to remain when the Cu content is less than 66 mass percent. On the other hand, when the content is higher than 76 mass percent, it gets difficult to perform the hot extrusion. Therefore, it is necessary for the Cu content to be 66 to 76 mass percent. Furthermore, in order to ensure the cold workability and the hot extrusion characteristics enough, it is preferable to be 68 to 75.5 mass percent.

[0044] In addition, as mentioned above, Si shows the grain refinement, strength improvement and inhibition function of stress-corrosion cracking by being added together with Zn. Accordingly, in the case that the grain refinement and strength improvement are the principal objects of third invention copper alloy used as wire drawing materials, it is necessary for the content of Si to be higher than 0.5 mass percent as well as in first invention copper alloy. Considering that said copper alloy is utilized as wire drawing materials, it is preferable to be higher than 0.8 mass percent and is the most preferable to be higher than 1 mass percent. However, when the Si content becomes higher than 2 mass percent, □ and/or □phases, a factor for obstructing cold workability, precipitate. Therefore, it is required to be less than 2 mass percent so that the cold workability is ensured, and, considering that plenty of Zn is present, it is preferable to be less than 1.8 mass percent, and more preferable to be less than 1.7 mass percent. Furthermore, in order to ensure the hot extrusion characteristics, cold workability and stress corrosion cracking resistance in third invention copper alloy, it is not sufficient enough to determine each contents of Cu, Si and Zn individually. Namely, it is necessary that the contents of Cu, Si and Zn are determined so as to satisfy the relationships Cu-5 · Si = 62 to 67 mass percent and Zn -6 Si = 32 to 38 mass percent. In other words, even though the contents of Cu, Si and Zn are in said range, the preferable hot workability can not be ensured when the contents of Cu, Si and Zn fit into the relationships Cu-5 · Si > 67 mass percent or Zn+6· Si < 32 mass percent. On the other hands, in case of Cu-5 · Si < 62 mass percent or Zn+6· Si > 38, the cold workability worsens because concentrations of Zn and Si at grain boundaries become higher, and because □ and □phases become easy to remain. Additionally, it becomes easy for the stress corrosion cracking to appear, and for some applications, dezincification is also caused easily.

[0045] In order to ensure enough the cold workability and stress-corrosion cracking resistance without these problems, it is preferable that the contents of Cu, Si and Zn are determined to satisfy the relationships Cu-5· Si = 63 to 66.5 mass percent and Zn + 6· Si = 33 to 37 mass percent.
Incidentally, grains grow with the rise of temperature or with time. During the recrystallization process, not the whole part of microstructure starts to recrystallize simultaneously, but some parts recrystallize faster than the others depending on its susceptibility. Therefore, it takes a long time for the whole structure to be completely recrystallized and the grains that recrystallize at the initial stage start to grow during that period. As a result, such grains become considerably large by the time the whole process finishes. Consequently, it is preferable to inhibit the growth of recrystallized grains during the recrystallization, so that the fine recrystallized grains distribute uniformly throughout the whole structure. Co has a function of inhibiting the growth of recrystallized grains, and this is the reason of Co addition in first to third invention copper alloys. In other words, Co combines with Si, and suppresses the growth of grains by forming fine precipitates (Co2Si of about 0.01 □m, etc.). In order that the Co shows the function of inhibiting the growth of grains, it is necessary for the Co content to be higher than 0.005 mass percent. All of the added Co is not associated with the formation of said precipitates but the solid solution part of Co improves the heat resistance of matrix and stress relaxation characteristic. Accordingly, in order that such functions of improving stress relaxation characteristic and heat resistance are shown enough, it is preferable for the Co content in all copper alloys of first to third inventions to be higher than 0.01 mass percent, and it is more preferable to be higher than 0.02 mass percent. On the other hands, when the Co addition becomes higher than 0.5 mass percent in the first and second invention copper alloys, and 0.3 mass percent in the third invention copper alloy, it is difficult to further improve the effect of grain-growth inhibition and the improvement effect of stress relaxation characteristic needed in applications because of saturation, and then it is proved uneconomical. Furthermore, there is a possibility that such additions lower the bending characteristics because of enlarging of precipitating particle and increasing of precipitating amount. Therefore, it is necessary for content of Co in the first and second invention copper alloys to be lower than 0.5 mass percent and for content of Co in the third invention copper alloy to be lower than 0.3 mass percent. However, in order to show effectively said functions and to ensure bending characteristics enough, it is preferable that the contents of Co in the first and second invention copper alloys become less than 0.3 mass percent, and it is more preferable that the contents become less than 0.2 mass percent. For the same reasons, it is preferable that the content of Co in the third invention copper alloy becomes less than 0.2 mass percent, and it is more preferable that the content becomes less than 0.15 mass percent.

[0046] In addition, since Co has the close relation with Si in grain refinement, the content of Co needs to be determined in relation to the content of Si. For the grain refinement to improve the strength required in applications, it is necessary that the ratio Co/Si in the first and third invention copper alloys is determined to be higher than 0.005 mass percent and the ratio Co/Si in the second invention copper alloy is determined to be higher than 0.02. In other words, when Co/Si dose not reach these values, there is a little formation of said precipitates and the effect of grain-growth inhibition is not shown, and then it is difficult to obtain the strength needed in applications of said invention copper alloys. Furthermore, in order to show the effect of grain growth inhibition enough and to further improve the strength it is preferable in the first and third invention copper alloys that Co/Si is higher than 0.01 and is more preferable that Co/Si is high than 0.02 mass percent. In addition, the preferable and more preferable values in the second invention copper alloy are higher than 0.04 and 0.06, respectively.

[0047] As described above, in the relation to Si content, Co content must be determined to satisfy the ratio of Co/Si, which becomes higher than the predetermined values. Said precipitates, however, become larger and increase, when Co/Si exceeds a certain level and then, the bending characteristics are obstructed. For example, when Co/Si in the first invention copper alloy used as the rolled materials becomes higher than 0.5 or Co/Si in the third invention copper alloy used as the wire drawing materials or their manufactured materials becomes higher than 0.4, the bending characteristics decreases suddenly. Additionally, even in the second invention copper alloy whose strength is not necessarily the same as required in the first invention copper alloy, when Co/Si exceeds 1.5, it becomes difficult to ensure the minimum requirement for the bending characteristics. Therefore, the upper limit of Co/Si must be determined by weighing the advantages and disadvantages as so far explained, as well as by considering the applications, processing history and the shapes required for these invention alloys. Concretely, the range of Co/Si is determined as follows: it is necessary that the upper limit of Co/Si in the first invention copper alloy satisfies the relationship Co/Si ≦ 0.5, and the preferable and optimum relationships are Co/Si ≦ 0.3 and Co/Si ≦ 0.2, respectively. In addition, in the second invention copper alloy, it is necessary to satisfy the relationship Co/Si ≦ 1.5, and the preferable and optimum relationships are Co/Si ≦ 1 and Co/Si ≦ 0.5, respectively. Furthermore, in the third invention copper alloy, it is necessary to satisfy the relationship Co/Si ≦ 0.4, and the preferable and optimum relationships are Co/Si ≦ 0.2 and Co/Si ≦ 0.15, respectively.

[0048] Fe and Ni show the similar effect of inhibiting the grain growth as Co (to be exact, its effect due to Fe and/or Ni is less than or equal to the effect of Co). Therefore, it is possible to contain Fe and/or Ni as a substitutive element of Co. Of course, further improvement of the effect can be expected by co-adding Fe and Ni together with Co. In the case that Fe and/or Ni are added in substitution for Co or with Co, those additions have the remarkable effect in economy because of decreasing the expensive Co content. As to the relationship (Co+Fe+Ni)/Si in the case of the additions of Fe and/or Ni, based upon the reason described above on the relationship Co/Si, the content of Fe or Ni is adjusted to be equal to the content of Co, and (Co+Fe+Ni)/Si is set to be equal to the value of Co/Si in the single addition of Co, in all of first, second and third invention copper alloys. In other words, the relationship (Fe+Ni+Co)/Si in the first invention copper alloy is 0.005 to 0.5 (preferably 0.01 to 0.3, more preferably 0.002 to 0.2), and said relationship in the second invention copper alloy is 0.02 to 1.5 (preferably 0.04 to 1, more preferably 0.06 to 0.5), and said relationship in the third invention copper alloy is 0.005 to 0.4 (preferably 0.01 to 0.2, more preferably 0.02 to 0.15). Incidentally, since Fe and Ni can become substitutive elements with the same function as Co, the total content in the case where two or three elements selected from a group of Fe, Ni and Co are added must be equal to the content of the single addition of Co (the content of Co as described above). However, in the case where two or three elements selected from Fe, Ni and Co are added, the upper limit of co-addition content of Fe, Ni and Co (total content) is permitted to be higher than the Co content by about 0.05 mass percent under consideration of the solid solution and precipitation. From said consideration, in the case where two or three elements selected from Fe, Ni and Co are co-added, it is desirable for the upper limit of total content (Fe+Ni+Co) to be set higher than the Co content by 0.05 mass percent. In other words, it is desirable that the total content (Fe+Ni+Co) in the first and second invention copper alloys is 0.005 to 0.55 mass percent (preferably 0.01 to 0.35 mass percent, more preferably 0.02 to 0.25 mass percent), and it is desirable that said total content in the third invention copper alloy is 0.005 to 0.35 mass percent (preferably 0.01 to 0.25 mass percent, more preferably 0.02 to 0.2 mass percent).

[0049] Sn shows the strength improvement function, grain refinement function and improvement function for stress relaxation characteristic, corrosion resistance and wear resistance, etc. In the first and third invention copper alloys, in order to show the strength improvement function, grain refinement function, improvement function for heat resistance in matrix and improvement function for stress relaxation characteristic, corrosion resistance and wear resistance, it is necessary that the Sn content is higher than 0.03 mass percent, and it is preferable to be higher than 0.05 mass percent. However, when the Sn content becomes higher than 1.5 mass percent in the first invention copper alloy used as rolled materials or 1 mass percent in the third invention copper alloy used as wire drawing materials, the bending characteristics decrease suddenly. Therefore, in order to ensure the bending characteristics, it is necessary that the Sn content in the first and third invention copper alloys is less than 1.5 mass percent and less than 1 mass percent, respectively. Additionally, in order to ensure the bending characteristics enough in both the first and third invention copper alloys, it is preferable for the Sn content to be less than 0.7 mass percent, and it is optimum to be less than 0.5 mass percent.

[0050] On the other hand, in the second invention copper alloy which has lower minimum strength requirement than the first and third invention copper alloys, it is preferable to try to improve the strength, grain refinement, stress relaxation characteristic, stress corrosion crack resistance, corrosion resistance and wear resistance, while considering the relation with Si content. Accordingly, it is necessary for the Sn content to be higher than 0.2 mass percent, and it is preferable to be higher than 1 mass percent and more preferable to be higher than 1.2 mass percent corresponding to required strength. However, when the Sn content exceeds 3 mass percent, the hot workability is obstructed, and then the bending characteristics decrease, too. Therefore, in order to ensure the workability, it is necessary for Sn content to be less than 3 mass percent, and it is preferable to be less than 2.6 mass percent so as to ensure more satisfactory hot-workability and bending characteristics, and more preferable to be less than 2.5 mass percent.

[0051] Additionally, in the case where Sn is added, it is necessary that its content is determined by considering the relationship with the Si content (Si/Sn). In the first invention copper alloy whose strength improvement is a principal purpose, when high strength is obtained with increase of Si content, ductility such as bending characteristics decreases remarkably for Si/Sn<1.5. Therefore, in the first invention copper alloy, it is necessary for the Sn content to satisfy the relationship Si/Sn ≧ 1.5. Furthermore, in order to ensure said ductility enough, it is preferable to satisfy the relationship Si/Sn ≧ 2, and it is optimum to satisfy the relationship Si/Sn ≧ 3. Moreover, in the third invention copper alloy where Sn content is suppressed to a little amount compared to the first invention copper alloy, for the same reasons described above, it is necessary for Sn content to satisfy the relationship Si/Sn ≧ 1. Furthermore, in order to ensure said ductility enough, it is preferable for the Sn content to satisfy the relationship Si/Sn ≧ 1.5, and it is optimum to satisfy the relationship Si/Sn ≧ 2.

[0052] On the other hand, in the second invention copper alloy where electric conductivity is required so as to be balanced with the strength, the addition of Si is restricted. Therefore, in order to ensure the high strength without losing the ductility, it is necessary for Sn content to satisfy the relationship Si/Sn ≦ 0.5. For more improvement of the ductility and strength, the preferable and optimum relationships are Si/Sn ≦ 0.4 and Si/Sn ≦ 0.3, respectively.
At least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf is added according as the applications of said alloys, and the effects mainly include the grain refinement, improvement of hot workability, improvement of corrosion resistance, function to render micro elements harmless unavoidably mixed into such as S, and improvement of stress relaxation characteristic, etc. Such effects are hardly expected in the case the content of each element is less than 0.003 mass percent, and on the contrary the effects expected from the additive quantity are not obtained in the case beyond 0.3 mass percent. Accordingly, the addition becomes useless in economy and rather results in losing the bending characteristics. However, in the third invention copper alloy with much Zn content, P, Sb and As are added specifically for the improvement of dezincification resistance and stress corrosion cracking resistance. Similarly to the case described above, the effects of P, Pb and As added for such purposes scarcely appear in the addition less than 0.005 mass percent. On the other hand, when the P content exceeds 0.2 mass percent, the cold bending characteristics are lost adversely. Therefore, for the additions of P, Sb and As in the third invention copper alloy, it is necessary for the contents to be 0.005 to 0.2 mass percent, and in the case of adding at least two elements from P, Sb and As, it is necessary for the total content to be 0.005 to 0.25 mass percent.

[0053] By the way, annealing is generally adopted for the heat treatment to obtain recrystallized materials (recrystallization treatment), where plastic worked materials mentioned in said (1) is kept at the temperature of 200 to 600 °C for 20 minutes to 10 hours. In the heat treatment usually carried out by batch processing system, when the time of heat treatment is long, the grains recrystallized at the early stage of heat treatment gradually grow, and then there is a possibility that the uniform grain refinement is obstructed, even if the effect of grain growth inhibition appears by the Co addition. However, in the case with such possibility, when the heat treatment (rapid heating treatment at high temperature) for the plastic worked materials is performed for a short time at higher temperature (body temperature of such worked materials) than general annealing temperature, the grain refinement due to the recrystallization by both Co addition and no addition is preferably carried out by the growth inhibition of early recrystallized grains. In other words, the recrystallization in many nucleation sites is realized by liberating the large thermal energy almost simultaneously in a short time, so as not to provide the grains with time to grow bigger. To be concrete, for example, the microstructure of said plastic worked materials is completely recrystallized by the heat treatment in the range from 450 to 750 °C for 1 to 1000 seconds.

[0054] In addition, the first, second and third invention copper alloys are generally produced as the recrystallized materials of (1), cold worked materials of (2) and manufactured materials of (3)(4), and alloy characteristics such as strength are improved more by adding the following treatment in the manufacturing process.

[0055] For example, in the case where a working rate in the cold working before obtaining the recrystallized materials is higher than 30 percent (preferably 60 percent), and more concretely when the rolling or wire drawing rate of the cold working in the process obtaining the plastic worked materials of (1) is higher than 30 percent (preferably 60 percent), the strength improvement due to the grain refinement is more effectively reached by promoting the refinement further. In other words, in order that grain refinement can be realized, the nucleation sites become necessary. As mentioned above, the nucleation sites increase by the cold working with the higher working rate, and the increment rate of nucleation sites becomes larger with increasing of working rate. Furthermore, since the recrystallization originates in the liberation of strain energy, finer grains are obtained by increasing shear strain through said cold working. As a result, the strength improvement due to the grain refinement is more effectively reached. Incidentally, it is preferable that the plastic worked materials on which the last recrystallization treatment is performed has small average size of grains, and concretely the average grain size is less than 20 □m (preferably less than 10 □m).

[0056] As the average grain size before recrystallization becomes small, the places where the recrystallized nucleation is based in the following heat treatment increase, and in particular, when dislocation density at the grain boundaries becomes higher, it is easy to form nucleation sites. However, since the strength increases with decreasing of the average grain size, the energy cost for manufacturing high strength copper alloy becomes expensive, and manufacturing time becomes longer. Therefore, it is preferable that the average grain size of plastic worked materials in (1) is determined from the balance with said working rate. In addition, when the recrystallized materials lack the strength required for the applications, these materials can obtain higher strength by performing the cold working or cold drawing with the working rate of 10 to 60 percent.

[0057] Furthermore, in the case where said plastic worked materials are obtained, when the rolling or wire drawing work of one path is performed, it is preferable that the rolling or wire drawing rate is set to be large (higher than 15 percent, preferably 25 percent). The further refinement of recrystallized grains can be realized by increment of the shear strain and nucleation sites resulting from the cold working with higher rolling and wire drawing rates. In addition, if the rolling is carried out by using the roll of small diameter or extremely large diameter, or if the wire drawing is carried out by wire dice with large dice angle or, by extremely small wire dice with large dice angle, the nucleation sites or the local distortion energy increases, so that the further refinement of recrystallized grain can be effectively realized. Furthermore, if the rolling is carried out by the rolling method with different peripheral speed, and in other words, if the rolling is carried out varying the velocity by use of the rolling machine providing with top and bottom rolls having different diameters, the large shear strain is given to the rolled materials, so that the grain refinement can be achieved. Additionally, in each invention copper alloy, depending on those applications, the spring elastic limit and stress relaxation characteristic can be remarkably improved by performing the suitable heat treatment (generally annealing in range of 150 to 600 °C for 1 second to 4 hours) without recrystallization. Concretely, heat treatment is carried out for the cold worked materials of (2) (including cold worked materials in (4)) or the manufactured materials of (3) (4), for instance, under the condition of 200 °C for 2 hours or 600 °C for 3 seconds.

EXAMPLES

[0058] As embodiment 1, the copper alloys of composition shown in tables 1 to 4 were melt in atmospheric air, and prism-shaped ingots of 35 mm in thickness, 80 mm in width and 200 mm in length were obtained. Intermediate plate materials of 6 mm in thickness were formed by hot rolling (four paths) of these ingots at 850 °C, and the materials after pickling became final plate materials of 1 mm in thickness by the cold rolling. Each final plate material was given the heat treatment (annealing) for one hour at the temperature causing the recystallization of 100 percent (called "recrystallization temperature"), so that there were obtained the first invention copper alloy from No.101 to No.186 by performing complete recrystallization treatment on the structure. Prior to the recrystallization treatment, samples (a square plate with one side of about 20 mm) picked up from each final plate material were annealed for one hour at each temperature rising with spacing of 50 °C starting from 300 °C, in order to find out the lowest temperature causing the complete recrystallization, so that such lowest temperature was determined as said recrystallization temperature of the samples (refer to Tables 15 to 17).

[0059] Furthermore, the final plate materials of the same quality (same form, same composition) as composing materials of alloy No.102, No.107, No.111, No.154 and No.180 were obtained due to the same process described above, and these final plate materials were recrystallized under a different condition from said condition, so that there were obtained the first invention copper alloy No. 102A, No. 107A, No.111A, No. 154A and No.180A with the same composition as No.102, No.107, No.111, No.152 and No.175, respectively. In other words, the first invention copper alloy No.102A, No.107A, No.111A, No.154A and No.180A were obtained by the recrystallization treatment (rapid heating treatment at higher temperature) in which the heating was maintained for a short time at much higher temperature than the given recrystallization temperature. The temperature a (°C) and heating time b (second) are shown as "a(b)" in the column titled "recrystallization temperature" in Tables 15 to 17. For example, "480(20)" in column of "recrystallization temperature" of No.102A in Table 15 means the heating at 480 °C for 20 seconds.

[0060] As embodiment 2, the copper alloys of composition shown in Tables 5 to 8 were melt in atmospheric air, and prism-shaped ingots of 35 mm in thickness, 80 mm in width and 200 mm in length were obtained. Intermediate plate materials of 6 mm in thickness were formed by hot rolling (four paths) of these ingots at 850 °C, and the materials after pickling became final plate materials of 1 mm in thickness by the cold rolling. Each final plate material was given by the heat treatment (annealing) for one hour at temperature causing the recystallization of 100 percent (by recrystallized treatment), so that there were obtained the second invention copper alloy from No.201 to No.281. In addition, the recrystallization temperature was determined in advance by the method similar to example 1 (refer Table 18 to 20).

[0061] Furthermore, the final plate materials of the same quality as composing materials of alloy No.202, No.209, No.250 and No.265 were obtained due to the same process described above, and these final plate materials were recrystallized by the above-described rapid heating treatment at higher temperature, so that there were obtained the second invention copper alloy No.202A, No.209A, No.250A and No.265A with the same composition as No.202, No.209, No.250 and No.265, respectively. In other words, the condition obtaining alloy No.202A, No.209A, No.250A and No.265A in the rapid heating treatment at high temperature ( a (°C) and heating time b (second)) is described as "a(b)" in column titled "recrystallization temperature" of Tables 18 to 20 by the same description as Tables 15 to 17.

[0062] As embodiment 3, the copper alloys of composition shown in Tables 9 to 12 were melt in atmospheric air, and column-shaped ingots of 95 mm in diameter and 180 mm in length were obtained. Round bars of 12 mm in diameter were obtained by extruding press (500 t) while heating the ingots at 780 °C. These round bars after pickling were worked by wire drawing into 8 mm in diameter, and after heat-treating the round bars for one hour at 500 °C and pickling them, the wires of 4 mm in diameter (molding materials) were obtained by wire drawing. Furthermore, each wire was heat-treated (annealed) for 1 hour at the temperature (recrystallization temperature) where recrystallization of 100 percent was realized (recrystallization treatment), and third invention copper alloys No.301 to 397 were obtained. For the recrystallization treatment, in advance, samples (wires of 20 mm in length (4 mm in diameter)) picked up from each wire were annealed for one hour at each temperature rising with spacing of 50 °C starting from 300 °C, in order to find out the lowest temperature causing the complete recrystallization, so that the lowest temperature was determined as said recrystallization temperature of the samples (refer to Tables 21 to 24).
Furthermore, the wires (molding materials) of the same quality as composing materials of alloy No.302, No.314 and No.338 were obtained due to the same process described above, and these wires were recrystallized by the above-described rapid heating treatment at higher temperature, so that there were obtained the third invention copper alloy No.302A, No.314A and No.338A with the same composition as No.302, No.314 and No.338, respectively. The condition obtaining alloy No.302A, No.314A and No.338A due to the rapid heating treatment at high temperature (temperature a (°C) and heating time b (second)) is described as "a(b)" in column titled "recrystallization temperature" of Tables 21 to 24 by the same descriptive method as Tables 15 to 17.
As comparative example 1, first comparative example alloys No.401 to No.422 shown in Table 13 were obtained on the basis of the same process as the first embodiment.
In addition, as comparative example 2, second comparative example alloys No.423 to No.431 shown in Table 14 were obtained due to the same process as third embodiment. Incidentally, the first comparative example alloys No. 401 to 407, respectively, have the same compositions as C2100, C2200, C2300, C2400, C2600, C2680 and C4250 of Japanese Industrial Standards (JIS), and the second comparative example alloys No.423 and 424 have the same compositions as C2600 and C2700 of JIS, respectively. Additionally, in Tables 1 to 12, the expression of "(Co+Fe+Ni)/Si" for alloys containing only Co without Fe and Ni is replaced by "Co/Si".

[0063] Incidentally, since the following problems in manufacturing process occurred for the comparative example alloys No.421, No.425, No. 427 and No.431, the manufacturing was abandoned because of impossibility of continuation thereafter. In other words, No.421 caused large cracking during the step where ingots were hot-rolled, and No.425 was not able to be hot-extruded. No.427 and No.431 ruptured in the wire drawing process. Accordingly, their manufacturing was abandoned because it is difficult to carry out the process thereafter.

[0064] For the first invention copper alloys of No.101 to 186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281 and No.202A, 209A, 250A, 265A, the third invention copper alloys of No.301 to 397 and No.302A, 314A, No.338A, and the first and second comparative example alloys of No.401 to 431 (except for No.421, No. 425, No. 427 and No. 431 which were abandoned the manufacturing), the average grain size D (□m) of recrystallized structures was measured on the basis of intercept method with the use of optical image (JIS-HO501). The results are shown in Tables 15 to 26.

[0065] For the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A and the first comparative example alloys No. 401 to 422 (except for No.421), the electric conductivity was measured. The results are shown in Tables 15 to 26 and Table 25. In addition, the electric conductivity (% IACS) is defined by a percentage of the ratio of the volume specific resistance of international standard soft copper (17.241×10^-9 µ Ω · m) divided by that of each alloy sample. Additionally, in the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A, the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A and the first comparative example alloys of No. 401 to 422 (except for No.421), proof stress (0.2% yield strength), tensile strength and elongation were measured by tensile test using an Amsler-type universal testing machine. Furthermore, after each alloy was cold-rolled to be as thin as 0.7mm, 0.2% yield strength, tensile strength and elongation of the rolled materials (called "post worked materials") were measured by the same tensile test as described above, and then evaluation of bending characteristics and stress corrosion cracking test were carried out. The results are shown in Tables 15 to 20 and Table 26.

[0066] In addition, for the first invention copper alloys of No.101 to No.186 and No.102A, 107A, 111A, 154A, 180A and the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A, 265A, it goes without saying that the post worked materials obtained by 30% rolling are also high strength copper alloy of the present invention.

[0067] In addition, the bending characteristics are evaluated from bending rate R/t at the cracking moment (R(mm): curvature radius of inner circumference side at the bending area, t(mm): thickness of tested plates.) This cracking occurred when the samples cut from the worked materials vertically to the rolling direction are bent in W shape.

[0068] In Tables 12 to 17 and Table 22, the test samples showing no cracks at R/t = 0.5 are indicated by a symbol ⊚ as superior bending characteristics. The pieces showing no cracks at R/t = 1.5 but found at 0.5 ≦ R/t<1.5 are indicated by a symbol ○ as preferable bending characteristics (there is no problem in practical use). The pieces showing no cracks at R/t = 2.5 but found at 1.5 ≦ R/t<2.5 are indicated by a symbol △ as general bending characteristics (there is problem in practical use but still usable). The pieces showing cracks at R/t = 2.5 are indicated by a symbol × as inferior bending characteristics (it is difficult to use).
In addition, testing of stress corrosion cracking is carried out by use of test container and testing solution pursuant to JISH3250, and characteristics of stress corrosion cracking resistance are evaluated from the relationship between ammonia atmosphere exposure time and stress relaxation rate (stress equivalent to 80% of the proof stress of the post worked materials is added on the surface of such post worked materials) by using the solution which is a mixture of aqueous ammonia and water in equal quantity. In Tables 15 to 20 and Table 25, the test samples showing the stress relaxation rate of less than 20% in the exposure for 75 hours are indicated by a symbol ⊚ as superior bending characteristics. The test samples showing the stress relaxation rate of higher than 20% in the exposure for 75 hours but less than 20% in the exposure for 30 hours are indicated by a symbol ○ as preferable bending characteristics (there is no problem in practical use). The test samples showing the stress relaxation rate of less than 20% in the exposure for 12 hours are indicated by a symbol △ as general bending characteristics (there is problem in practical use but still usable). The test samples showing the stress relaxation rate of higher than 20% in the exposure for 12 hours are indicated by a symbol × as inferior bending characteristics (it is difficult to use).

[0069] Additionally, in the third invention copper alloys of No.301 to 397 and No.302A, 314A and 338A, the second invention copper alloys of No.423 to 431 (except No.425, No.427 and No.431 of abandoned manufacture), proof stress, tensile strength and elongation are determined from tensile testing with use of an Amsler-type universal testing machine.

[0070] Furthermore, each alloy is wire drawn to 3.35mm in thickness, and proof stress, tensile strength and elongation in the wire drawing materials (called "post worked materials") are determined by the same tensile testing as being described above. Additionally, evaluation of bending characteristics and testing of stress corrosion cracking are carried out. The results are shown in Tables 21 to 24 and Table 26. In addition, the post worked materials are obtained by the wire drawing of the third invention copper alloys of No.301 to 397 and No.302A, 314A and 338A and the second invention copper alloys of No.201 to 281, No.202A, 209A, 250A and 265A, and it goes without saying that such post worked materials are also the high strength copper alloy of the present invention.

[0071] Additionally, the bending characteristics were evaluated from bending rate R/d when the post worked materials were bent to 90 degree by use of V-block, and the cracking was caused (R (mm): curvature radius of inner circumference side at the bending area, d (mm): radius of post worked materials). In Tables 18 to 22, the pieces showing no cracks at R/d = 0 are indicated by a symbol ⊚ as superior bending characteristics. The pieces showing no cracks at R/d = 0.25 but found at 0 ≦ R/d<0.25 are indicated by a symbol ○ as preferable bending characteristics (there is no problem in practical use). The pieces showing no cracks at R/d = 0.5 but found at 0.25 ≦ R/d<0.5 are indicated by a symbol △ as general bending characteristics (there is problem in practical use but still usable). The pieces showing cracks at R/d = 0.5 are indicated by a symbol × as inferior bending characteristics (it is difficult to use).

[0072] In addition, the stress corrosion cracking test using the post worked material used for the evaluation of bending characteristics with R/d=1.5 and 90 degree bending is carried out by use of test device and test liquid pursuant to JISH3250. After the exposure in ammonia using the solution which is a mixture of aqueous ammonia and water in equal amount and pickling, the stress corrosion cracking resistance was evaluated by investigating the cracking existence using the stereoscopic microscope with 10 times magnification. In Tables 15 to 20 and Table 25, the pieces showing no cracks in the exposure for 40 hours are indicated by a symbol ⊚ as superior corrosion cracking resistance. The pieces showing cracks in the exposure for 40 hours but not found in the exposure for 15 hours are indicated by a symbol ○ as preferable corrosion cracking resistance (there is no problem practical use). The pieces showing cracks in the exposure for 15 hours but not found in the exposure for 6 hours are indicated by a symbol △ as general corrosion cracking resistance (there is problem in practical use but still usable). The pieces showing cracks in the exposure for 6 hours are indicated by a symbol × as inferior stress corrosion cracking resistance (it is difficult to use).

INDUSTRIAL APPLICABILITY

[0073] As understood from Tables 15 to 26, in comparison with first and second comparative example alloys having neither alloy composition nor recrystallized structure specified at the beginning (of this specification), it becomes possible for the first to third invention copper alloys to realize the grain refinement and to improve greatly the machinability and bending characteristics. It is possible for the present invention alloy to be used preferably as plate, rod and wire materials even in difficult applications in which the prior high strength copper alloys cannot be used. In addition, it is possible to obtain the grain refinement and strength improvement by the recrystallization treatment due to the rapid high temperature heating processes. Furthermore, though not shown in Tables 15 to 26, as regards said post obtained from the rolled materials and wire drawing materials after the recrystallization, by cold rolling and wire drawing) heat-treated for 1 second to 4 hours at 150 to 600 °C, it was confirmed that spring deflection limit and stress relaxation characteristics are greatly improved.

TABLE 21

Alloy	Mean grain size	Recrystallization temperature	Mechanical properies			Mechanical properies (Post workpiece)			Bending characteristics (Post workpiece)	Corrosion cracking resistance	Electroconductivity
No.	(µm)	(°C)	Proof stress (N/mm2)	Tensile strength (N/mm2	Elongation (%)	Proof stress (N/mm2)	Tesile strength (N/mm2)	Elongation ( %)			(%IACS)
301	3,1	300	310	502	38	635	729	6	○	Δ	13
302	3,2	300	324	518	35	658	756	6	○	Δ	13
302A	3,0	500(15)	339	527	37	670	765	7	○	Δ	13
303	2,9	350	345	533	35	673	768	6	○	Δ	13
304	2,8	350	352	540	35	685	775	6	○	Δ	13
305	2,9	300	340	535	36	685	776	6	○	○	12
306	3,3	350	266	453	39	589	667	7	○	Δ	16
307	2,9	350	305	495	36	621	717	6	○	Δ	15
308	2,7	350	332	526	34	670	762	6	○	Δ	13
309	2,2	350	360	541	32	677	774	5	Δ	○	14
310	2,4	350	372	569	35	713	824	6	Δ	○	12
311	2,3	350	382	580	32	729	841	5	Δ	○	12
312	1,9	350	392	580	34	751	860	5	Δ	○	11
313	2,6	350	346	541	35	682	784	6	○	Δ	13
314	2,4	350	360	556	35	716	811	6	Δ	○	12
314A	2,3	550(10)	372	565	36	725	817	7	○	○	12
315	2,3	350	375	567	36	728	819	6	○	○	12
316	2,3	350	376	569	36	733	822	6	○	○	12
317	2,7	350	338	533	35	670	773	6	○	Δ	12
318	2,4	400	349	546	32	694	792	5	○	○	12
319	3,4	300	253	433	39	559	638	7	○	Δ	17
320	2,7	350	339	535	36	675	776	6	○	○	12
321	3,4	350	255	443	38	568	647	6	○	Δ	16
322	2,1	400	377	574	35	726	832	5	○	○	11
323	2,8	350	342	537	35	685	788	6	○	Δ	12
324	2,6	350	358	555	34	702	805	5	○	○	12
325	2,8	350	293	481	34	615	702	6	Δ	Δ	18
326	2,4	350	353	548	35	803	807	6	○	○	12

Claims

1. A high strength copper alloy characterized in that said copper alloy consists of 4 to 17 mass percent of Zn, 0.1 to 0.8 mass percent of Si and the remaining mass percent of Cu, wherein said mass percent of Zn and said mass percent of Si satisfy the relationship Zn-2.5 · Si=2 to 15 mass percent; average grain size D of the microstructure of said copper alloy distributes in 0.3 µm ≦ D ≦ 3.5 µm; and 0.2% yield strength in recrystallization state of said copper alloy is higher than 250N/mm².

2. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.005 to 0.5 mass percent of Co, wherein said mass percent Co and said mass percent of Si satisfy the relationship Co/Si=0.02 to 1.5.

3. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.2 to 3 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn ≦ 0.5.

4. The high strength copper alloy according to Claim 2, wherein said copper alloy contains 0.2 to 3 mass percent of Sn, wherein said mass percent of Sn and said mass percent of Si satisfy the relationship Si/Sn ≦ 0.5.

5. The high strength copper alloy according to Claim 1, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent ofNi, wherein said mass percent of Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.02 to 1.5.

6. The high strength copper alloy according to Claim 3, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent of Ni, wherein said mass percent Fe, said mass percent of Ni and said mass percent of Si satisfy the relationship (Fe+Ni)/Si=0.02 to 1.5.

7. The high strength copper alloy according to Claim 2, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent ofNi, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.02 to 1.5.

8. The high strength copper alloy according to Claim 4, wherein said copper alloy contains 0.005 to 0.3 mass percent of Fe and/or 0.005 to 0.3 mass percent ofNi, wherein said mass percent of Fe, said mass percent of Ni, said mass percent of Co and said mass percent of Si satisfy the relationship (Fe+Ni+Co)/Si=0.02 to 1.5.

9. The high strength copper alloy according to any one of Claims 1 through 8, wherein said copper alloy contains at least one element selected from a group of P, Sb, As, Sr, Mg, Y, Cr, La, Ti, Mn, Zr, In and Hf, wherein content of said element is 0.003 to 0.3 mass percent.

10. The high strength copper alloy according to any one of Claims 1 through 9, wherein said copper alloy is recrystallized material obtained from recrystallization of plastic worked material, which is formed by plastic working including cold working with working rate being more than 30 percent.

11. The high strength copper alloy according to Claim 10, wherein said copper alloy is recrystallized material obtained by heat-treatment of said plastic worked material at the range from 450 to 750 °C for 1 to 1000 seconds.

12. The high strength copper alloy according to Claim 10, wherein said copper alloy is cold rolled material obtained by cold rolling or cold drawing of said recrystallized materials.

13. The high strength copper alloy according to Claim 12, wherein said copper alloy is obtained by heat-treatment of said cold worked material at the range from 150 to 600 °C for 1 second to 4 hours.

14. The high strength copper alloy according to Claim 12, wherein said copper alloy is manufactured material obtained by working said cold worked material into a predetermined form.

15. The high strength copper alloy according to Claim 14, wherein said copper alloy is obtained by heat-treatment of said manufactured material at the range from 150 to 600 °C for 1 second to 4 hours.

16. The high strength copper alloy according to any one of Claims 1 through 9, wherein said copper alloy is rolled material or its manufactured material by working said rolled material into a predetermined form.

17. The high strength copper alloy according to any one of Claims 1 through 16, wherein said copper alloy is wire drawing material or its manufactured material by working said wire drawing material into a predetermined form.